gawd... that's an awfully cumbersome way of doing things.
Never use getdammage to check if a unit is alive. It's probably about the most unreliable method there is...
Normally I'd say use not (alive
unit), but because we're dealing with tanks you're better to use not (canmove
tank) or not (canfire
tank).
So, in one trigger try this as the condition field:
"not (canmove _x) or not (canfire _x)" count [
tank1, tank2, tank3, tank4, tank5, tank6 ] == 6
That detects when all the tanks are disabled (can't fire or move).
You can have as many tanks as you want in the array, provided you change the number at the end to equal the number in the array